I'm sorry if this has been answered before, but I feel like I have tried all the solutions and nothing seems to be working.
When I put the drag and drop code into a plain composition with nothing else on the timeline, it works perfectly.
As soon as I have anything else on the timeline a weird offset happens when dragging and dropping.
Please check out my solution here:
remove left top in timeline.
If you have animation of your objects on the timeline this will cause problems. If you need some animation of your draggables then it needs to be done inside the symbol.